Art of lubrication



Patented May 9, 1944 UNITED STATES, PATENT OFFICE I ART oF f rl cATloN .Willard L. Finley, James H. Kir

' No Drawing.

Edgewood Arsenal, Md, and

k, Hammond, Ind., aosignora to Y Sinclair Refining Comp corporation of Maine Application Amst Serial No. 407,440

any, New-York, N. Y., a

4 Claims. (Cl. 252-48) contain from 4 to 6 carbon atoms and alkyl esters of salicylic acid of which the alkyl groups contain from 6 to 18 carbon atoms, and more particularly the mixed calcium. salts of tertiaryalkyl phenol sulfides of which the alkyl groups contain from 4 to 6 carbon atoms and iso alkyl esters of sallcylic acid of which the alkyl group contains from 6 to 18 carbon atoms, the addend being present in amount .insuflicient materially to alter the normally liquid character of the petroleum lubricatins oil base.

The trend of development in internal combustion engines has imposed increasing burdens upon the oils used for their lubrication, particularly with respect to the operating temperatures and pressures. Extreme requirements in both of these respects are represented by the Diesel type of engines and supercharged aircraft engines. The useful operating life of a lubricating oil, in such severe services, is determined in large measure by its thermal stability and by its physical capacity to continue functioning as a lubricant at the high temperatures and pressures encountered. The use of special alloy bearing metals, to permit the use of increased bearing pressures and consequently smaller bearing surfaces, adds to these burdens both in that such metals, in contact with the oil, frequently tend to accelerate degradation of the petroleum lubricating oil base and in that lubricating oils and lubricating oil compositions which have the requisite properties in other respects frequently tend to be corrosive with respect to such metals. One measure of thermal stability is resistance to oxidation. Oxidation promotes either the formation of sludge or the formation of acids corrosive to hearing metals, or both. To have any real meaning, this measure of thermal stability must be appliedunder conditions of service since, for example, bearing metals may promote oxidation. In another aspect, thermal stability is determined not only by the extent of oxidation or decomposition but also by the character of the products of such decomposition or oxidation and by the extent and location,

within the engine, of deposits of such products. sludge, coke and resinous vamish-like materials, for example.

In previous applications, Serial No. 368,992, flied December '7, 1940, and Serial No. 407,002, filed August 15, 1941, the compounding of petroleum lubricating oils with calcium salts of alkyl esters of salicylic acid including the normal alkyl esters and the isoalkyl esters have been described. The addends described in those applications function as strong anti-oxidants effective to inhibit, over prolonged induction periods, the rate of oxygen absorption at elevated temperatures and thus to limit any corrosive tendencies of the lubricating oil compositions with respect to hearing metals, to render deposits of sludge and "carbon" within the engine soft and friable rather than hard and coherent, and to act as a solvent for sludge formed and thus to disintegrate and remove any deposits of sludge and carbon as an incident of normal engine operation.

These valuable properties of the calcium salts of alkyl esters of salicylic acid, however, are rapidly impaired or oven destroyed bythe presence in the lubricating oil composition, under service conditions, of metallic soaps suchas those formed by corrosion of bearing metals through reaction with acid oxidation products of the lu bricating oil composition. The use of alkyl phenol sulfides, inclu in polymers and polysulfides, as addends in the compounding of petroleum lubricants has been described. Such addends have little if any direct effect as anti-oxidants, and they tend to accelerate sludge formation, but they do function to protect metals with respect to corrosion, to inhibit the solution of metals in the In.- bricating oil composition, to precipitate or otherwise to deactivate any dissolved metal and particularly to minimize the pro-oxidant effect of i any dissolved'metal. We have now combined the desirable functions of these two types of addends to secure new advantages from the combination and to avoid the disadvantages and limitations'of either used alone.

We have found that such alkyl phenol sulfides and such alkyl esters of salicylic acid can be combined with lime to form mixed salts, the addends incorporating in the lubricating compositions of our-invention, which are p w rful anti-oxidants.

which inhibit corrosion or solution of metals,

which deactivate dissolved metals, which are powerful detergent-dispersion agents, which inhibit viscosity rise and which contribute to the film strength of petroleum lubricating oil compositions in which they are incorporated. The octyl ester of salicylic acid, for example. may be represented by the following formula: a

COOCgHu The amyl phenol polysulfide, for example, may

be represented by the following formula:-

In the addends incorporated in the lubricating compositions of our invention, a phenolic hydrogen in each of these compounds is replaced by a calcium bond to form a mixed calcium salt which may be represented by the following formula:

on "by HnClOOCO Q IQ 0H1: lHn

O-Ca-O can be formed directly by reacting lime with a mixture of the alkyl ester of salicylic acid and the alkyl phenol sulfide. The reaction is with advantage carried out in a solvent, and lubricating oil compatible with the ultimate lubricating oil composition, or compositions is an advantageous reaction medium. The reaction is with advantage carried out with a suiilcient excess of the alkyl ester of salicylic acid so that the addend composition, and the petroleum lubricating oil composition in which it is incorporated, will include a proportion of the calcium salt of the alkyl ester of salicylic acid somewhat larger than the proportion of the mixed calcium salt of the alkyl phenol sulfide and the alkyl ester of salicylic acid. The excess oi the calcium salt of the alkyl ester of salicylic acid may be in the form of the neutral salt or a mixture of the neutral and basic salts. The reaction is with advantage carried out at a temperature below that-at which substantial conversion of the compound in which the calcium replaces phenolic hydrogen to: compounds in which the calcium replaces carboxylic hydrogen or alkyl groups takes place. At maximum temperatures of about 280 F. this conversion is negligible but at temperatures up wards of about 300 F. it proceeds with increasing rapidity. The total proportion of calcium salts of the alkyl esters of salicylic acid in the lubricating oil compositions of our invention may approximate, with advantage, from about 1% to about 5% by weight on the composition, and oi this the mixed calcium salts of the alkyl esters of salicylic acid and the alkyl phenol sulfides may, with advantage, approximate a proportion equivalent to from about 0.2% to about 0.5% of the alkyl phenol sulfide.

While the addend'incorporated in the lubricating compositions of our invention can be prepared as a separate product, for example in solvents such asbenzene or toluene or petroleum hydrocarbonsiwe have found it advantageous to produce the addend by reaction in the petroleum lubricating oil base of the lubricating composition in which it is to be incorporated. For example, we add 1%, 2%, 3% or somewhat more of the neutral calcium salt of the alkyl ester of salicylic acid, or of a mixture of the neutral and basic calcium salt of the alkyl ester of salicylic acid, to the petroleum lubricating oil base, or a portion of it, then add from about 0.2% to about 0.5% of the alkyl phenol sulfide to this mixture and then dehydrate the composite at a temperature not exceeding about 280 F. under a vacuum if necessary. Or, for example, we add the equivalent proportions of the alkyl ester of salicylic acid and of the alkyl phenol sulfide and the reacting proportion, or somewhat more, of lime as calcium hydroxide to the petroleum lubricating oil base, or a portion of it, and then dehydrate the composite in the same manner. The following lubricating oil compositions embodying our invention will illustrate its application:

I II III 26.8 27.0 430 430 490 400 565.4 600.2 67.7 69.5 90.3 90.1 our F 0 5 0 Carbon residue (ash-free) percent. 96 1. 19 l. 20 Ash 0.07 0.60 0.01 Color NPA 4 6++ 7(4%) 7-(4%-) In the foregoing compositions, the addends consisted of the reaction product of a mixture of the neutral and basic calcium salts of the iso octyl ester of salicylic acid in which the basic salt comprised from about one-fifth to about one-half of the mixture and tertiary amyl phenol sulfide in polymerized form and containing polysulfide sulfur. In Example I, the reaction product of 4% of the calcium salt of the iso octyl ester of salicylic acid and 0.25% of the tertiary amyl phenol sul-- fide was incorporated in a pale oil blend derived from a South Texas crude. Examples II and III were a Pennsylvania motor oil (SAE 30) containing the reaction products, respectively, of 4% of the calciumsalt and 0.5% of the sulfide and 4% of the calcium salt and 0.25% of the sulfide. All of the compositions of the foregoing examples were basic in reaction.

CHCh insoluble -.d

aseaaoi compounded as Just described, lubricating oil compositions of our invention, after addition of 0.01% FezO: as iron naphthenate as a pro-oxident, have shown bearing corrosion measured by loss of metal ranging from nothing up to 0.005 gram under test conditions (the "Underwood oxidation test") such that the loss from the same lubricating oil base, without the addends but a with the addition 01' the same proportion of the same pro-oxidant, ranged from 1.454grams to 1.894 grams with cadmium silver bearing metal. Similar comparisons, based on identical tests, have shown that our improved results are not secured with either the calcium salt. of the alkyl ester of salicylic acidor the alkyl phenol sulfide used alone, uncombined. Petroleum lubricating compositions embodying our invention also exhibit a marked increase in sludging time as indicated by the Indiana oxidation test." For example, with a petroleum oil base such as that of Example I, the sludging time was increased from 22.5 hours to 35 hours by incorporating the reaction products of 1% of the calcium salt and 0.5% of the sulfide and to 60 hours by incorporating the reaction products of 3.5% of the calcium salt and 0.5% of the sulfide. with -a petroleum oil base suc has that of Examples II and III, the sludging time was increased irom 200 hours to 365 hours by incorporating the reaction products of 3% of the calcium salt and 0.25% of the sulfide, and to 480 hours by incorporating the reaction products of 4% of the calcium salt and 0.5% of the sulfide."

The benefits derived from the presentinvention are gurther illustrated by the following tabulated results ofidentical comparative tests (the Underwood oxidation test) applied to Sample A, an uncompounded oil of the type used in the previous Example I, and to Sample B, the same base oil containing the reaction products of 3.5% of the calcium salt and 0.5% of the sulflde. To each sample 0.01% of F8203 as iron naphthenate was. added as a pro-oxidant.

Sample A Sample B e eaa W...

at n no Vlscosi at 210 IL.

gas a Oil i'sts alter 10 hours:

P." FFP'EN P!" sm r- 9 s: as 8@ 22 as gas a g s 9 9. 9 pp rr as gas a- 2 Similarly,

3 ing oil composition and corrosion of bearing metals resulting from oxidation in the presence of the bearing metals under severe service conditions. a

The advantages derived from the present invention, with respect to diminished carbon or like deposits within the cylinders of internal combustion engines and bearing corrosion losses, are illustrated by the following tabulated results of comparative tests (Bus engine sludglng test") wherein the oil is subjected to conditions closely approximating those encountered in actual use. The apparatus used in these tests consists of a metal box or sump adapted to hold a pool of oil which is heated by an oil bath in which the box is suspended. The box is provided with a cover heated by a lead bath. A rotary paddle wheel is supported within the box so that in rotating the blades thereof dip into the oil pool and throw the oil onto the sides and cover of the box and also onto an alloy bearing suspended in the box above the surface of the pool of oil. The cover and upper portion, of the sides of the box are partially shielded from the oil thrown from the paddle wheel by a screen of 30-mesh iron screen wire.

In carrying out this test, the temperature of the oil in the sump is maintained at 250 F., and the temperature of the lead bath is maintained at 500 F. The paddle wheel is rotated at 750 R. P. M. and air is blown through the chamber at a rate of 1 cubic foot per minute. The test is divided into 2 periods of 150 hours each. In starting the test, 2 liters of oil are placed in the sump. At the end of the first period, the oil is drained from the sump and new oil added together with 10% of the oil used in the first period of the test. At the end of each period the amount of corrosion of the bearing was determined by the loss of weight thereof and, at the end of the second period, the amount of carbon deposited on the lead-bath-heated-cover oi the apparatus was determined and the condition of the oil and of the walls of the chamber noted.

In these tests Sample Cwas an uncompounded oil of the type used in the previous Examples II and III and sample D was the same type of 011 containing the reaction products of 4% of the calcium salt and 0.5% of the sulfide. The results of these comparative tests were as follows:

1 Alkaline.

The high solvent, or detergent-dispersion,

The stability of the oil as represented by the oxygen absorption test is greatly improved by the incorporation in the oil of the mixed salts of the present invention. This is illustrated by the following tabulations of comparative results in which Sample E is an uncompounded Pennsylvania motor oil (SAE 30) of the type used in Examples II and III and Sample F is the same oil having compounded therewith the reaction products of 1% of the calcium salt and 0.25% of the sulfide. The results of the tests are reported in terms of number of minutes required for the absorption of the indicated cubic centimeters the presence of copper-lead alloy bearings and under comparable conditions.

C. C. of oxygen/100 grams of oil 8smple 132 Sample F Minutes Minutes Further, our improved lubricating oil compounds, have given remarkable results in actual service. For example, a compound consisting of a, Pennsylvania motor oil (SAE 30) having a viscosity of 63 at 210 F., containing the reaction products of 3% by weight of the calcium salt oi the iso-octyl ester of salicyclic acid and 0.25% of the sulfide has satisfactorily lubricated the Diesel engines of eight large stream-line locomotives of one railway company for upwards of 500,000 engine miles with a 30,000 mile drain period. On another railroad, our improved lubricant, consisting of a. pale oil blend derived from a South Texas crude, containing the reaction products of 4% of the calcium salt and 0.25% of the sulfide, has satisfactorily lubricated the Diesel engine of a large streamline locomotivefor a distance upwards of'65,000 miles without change of crankcase oil.

We claim:

1. A liquid lubricating oil composition comprising a petroleum lubricating oil and. a minor proportion of a mixed calcium salt of an alkyl ofoxyszen at normal temperature and pressure per 100 grams or oil. Each sample was tested in phenol sulfide of which the alkyl groups contain from four to six carbon atoms and an alkyl ester of salicyclic acid of which the alkyl groups contain irom six to eighteen carbon atoms.

2. A liquid lubricating oil composition comprising a petroleum lubricating oil and a minor proportion of a mixed calcium salt of a tertiary alkyl phenol sulfide of which the alkyl groups contain from four to six carbon atoms and an iso alkyl ester of salicyclic acid of which the alkyl groups contain from six to eighteen carbon atoms.

3. A liquid lubricating oil composition comprising a petroleum lubricating oil, a minor proportion of a calcium salt or an alkyl ester of salicyclic acid of which the alkyl groups contain from six to eighteen carbon atoms and a smaller proportion of a mixed calcium salt of an alkyl phenol sulfide of which the alkyl groups contain proportion of a mixed calcium salt of a tertiary alkyl phenol sulfide of which the alkyl groups contain from four to six carbon atoms and an iso alkyl ester of salicyclic acid of which the alkyl groups contain from six to eighteen carbon atoms.

WILLARD L. FINLEY. JAMES H. KIRK. 

